It forms from the shield. In one of the recent Action Comics issues you see the suit materialize from the shield and then when he arrives home the suit de-materilizes back into the shield and he removes that from his chest.

Yeah, but in that drawing the top was already there, and the rest materialized afterwards.

So, he might wear the shield directly on the chest underneath? Or the beltbuckle? They're lodged into the skin somehow?
It's not really clear. I hope it wont be as halfassed in the movie.

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